This invention relates to the field of non-destructive, comparative metal tests, especially those in which it is desired to ascertain whether a given coin has identical metallic content in identical proportions, to coins of the same type which are known to be genuine. While coins of obviously counterfeit nature can be readily detected by physical examination or density tests, clever counterfeiters have produced gold coins of exceptionally authentic appearance and density, but have alloyed the metal with non-precious metals, or used the non-precious metals as internal slugs to cheat on their gold content. The device described herein will readily detect any counterfeit coins in which the metal content and proportions are not those of a genuine coin.